If you've been hearing or reading a lot about blockchain but you still aren't entirely certain how to define it, you're not alone. It's something that Jack Dorsey, the chief executive officer and chairman of Square (and CEO of Twitter), describes as the "next big unlock," something that, he notes, is normally applied to accounting terms but has the potential to "be applied to so much more."

In an interview earlier this week at the Computer History Museum in Mountain View, California, I had the chance to ask Dorsey about Square's business, the future of banking, cryptocurrencies, blockchain, and more.

Blockchain is often defined as a ledger that enables secure, encrypted transactions. Some financial and technical experts have described it as analogous to the early days of the internet: it's a framework or backbone for transactions, while the various use cases for it are analogous to apps on the internet as we know them today.